Rapid, accurate long-range detection of hazardous chemical/biological target agents including environmental toxins remains a formidable problem. In the military sector, early warning is necessary to protect troops from battlefield releases of chemical and biological weapons. This requires the ability to perform stand-off detection, identification, and quantification of the composition of the releases at distances ranging from 1 to 150 km or more. Such analysis must be performed quickly enough to permit personnel to either evacuate their position or deploy some other appropriate protective measure such as putting on a gas mask and/or protective clothing. In the industrial sector, rapid identification and quantification of chemical spills and/or accidental releases from chemical plants and the like is critical for protecting the well-being of surrounding residents. In both sectors, rapid and efficient containment and remediation of the chemical/biological release is desired to minimize the spatial extent of the release and to destroy the active hazardous species. This is particularly crucial for typical battlefield scenarios in which chemical and biological weaponry may be rapidly deployed.
To date, attempts at achieving long-range detection of chemical and biological agents have been only moderately successful. The current technique-light detection and ranging (LIDAR) with differential absorption (DIAL) has been employed for detection of warfare agents. DIAL systems are remote sensing devices that use a laser to illuminate a body or target. An optical system collects the backscattered radiation to derive target information, such as spectral reflectance/absorption, fluorescence, Raman scattering, or phosphorescence. In one example, LIDAR was used to detect tryptophan fluorescence as an indicator of biological agents.
LIDAR and DIAL chemical and biological techniques do have several important features for detection of agents. They have long-range transmission in atmospheric window regions and rapid response; hardware is readily available. LIDAR and DIAL can look at very narrow wavelength regions for specificity and observe individual molecular absorption lines while DIAL uses multiple wavelengths to enhance selectivity.